M1078 charging problem

[johnturley]

The dual voltage alternator on my M1078 was working perfectly for months then suddenly burned up the alternator in a 5 mile drive. I checked the batteries, they were fully charged, no shorts and in perfect condition. I replaced the alternator and regulator and it shows perfect 14 volt and 28 volts but charges 100 amps continuously. The alternator heats up immediately. Can anyone help with this problem?

 

[Suprman]

Check for shorts along the wires and there is a load control reverse polarity box under the spare tire thats a possible culprit

 

[Ukraine Train]

I'm new to these trucks so I'm not sure how much help I can offer, but I would maybe try to remove the breakers for as many devices as possible and see if the high draw goes away with one of them. If you power the truck on but don't start it, do you see the same high current flow from the batteries?

 

[Oxyacetylene]

How do you know it is putting out 100 amps continuously? Are you using a clamp meter? For something to draw that much current there has to be a big malfunction, maybe the load control unit like Suprman suggested.

 

[johnturley]

We did check it with a clamp meter and both 12 and 24 are putting out max amps. We had no load on the truck only the engine running. We checked the wiring and found no shorts. Is there a procedure on checking the reverse polarity relay that will not damage any other electrical component or just replace it and who sells it.

 

[Suprman]

I wouldnt run it like that you will cook another alt. Measure the regulator voltages in comparison to the alt output voltage. There really isnt anything on the truck that should draw high current. Get to the box under the cab and see whats going on. You could have a shorted battery or something like that. The 12 and 24 volt systems are really one 24 volt system with a tap off the alternator mid way and a tap between the batteries. I think the box under the spare tire is just a diode bank like a battery isolator its actually called a reverse polarity relay in the manual. You may be able to disconnect the batteries and meter it out see if one of the terminals is internally shorted. Feel it see if its getting hot.

 

[Suprman]

Just thinking if you had access to a flir cam you could look over the whole truck for hot spots. That much current is going to make something warm.

 

[johnturley]

The only thing so far we have been able to tell that gets hot is the alternator the old one caught on fire. The new one came with a new voltage regulator. Found the relay in the dash panel that is K-11 Excitation. This is on when the truck is on but don't know what activates it I replaced it also. When this is removed the alternator does not engage. We check all 4 batteries and they are reading good on the battery tester meter

 

[Suprman]

The alternator needs an exciter voltage to start making voltage. You need to look for heat and find where that high current is being drawn. You can have one of the mail power wires worn thru somewhere. It could be alot of things. Disconnect the batteries and start ohm metering things out to ground. Its not going to be a dash relay 100 amps would melt the relay. The manual isnt going to help you that much on this one you need to troubleshoot.

 

[johnturley]

I understand that K11 does not handle the 100 amps do you happen to know where it gets signal from to activate the relay to activate the alternator. Is there another component that might be malfunctioning that is giving the alternator a false reading causing it to stay activated.

 

[Suprman]

The alternator makes electricity when the truck is running. The exciter relay appears to be functioning properly. You have a damaged component somewhere or a wire worn thru causing a short creating a large load on the alternator. What is the voltage at the 12v alt output, 24v alt output both with the engine off. Start the truck and measure again. Then measure the voltage at the regulator 12v and 24v. Post all results. Then go to the batteries and measure the voltage across them with the truck off and then with the truck running. Post the results. Then we can go from there.

 

[Shark Bait]

I found this a while back but I hadn't got to verify any of it. Maybe it'll help someone out and let us know.

Dave

 

[johnturley]

We might have fixed it we will check it on Monday we had some corrosion on the 24 v terminal on the reverse polarity module. the last check on Friday the alternator was putting out little to no amps will run it again on Monday to see if problem has been fixed. Thanks for all the help I will let you know f it is fixed

 

[bikeracer917]

Hi. Was wondering if this might have something to do with your problem...I keep getting problem with the gages not working. Such as oil pressure and Speedo and 24volt and 12 volt gages as well as the alternator not charging. Once I unplug the connection to the crisis everything works... Does anyone know what the solution to this problem is?

 

[bikeracer917]

Freaking phone... Crisis was supposed to be c.t.i.s.

 

[Suprman]

Check all the dash harnesses. Look at the alternator running make sure both lights on the regulator are flashing green. Could be a bad cits ecu the easiest way to rule it out is to swap in a known good one, make sure the ctis ecu has a good ground. Under the relay breaker panel right side is a ground make sure its on good you may want to add a star washer. Check all dash grounds. Measure alt output and voltage at batteries. The trucks get funny with under voltage.